Single-crystal – oriented-crystal – and epitaxy growth processes; – Apparatus – For crystallization from liquid or supercritical state
Patent
1993-05-19
1994-12-20
Breneman, R. Bruce
Single-crystal, oriented-crystal, and epitaxy growth processes;
Apparatus
For crystallization from liquid or supercritical state
117 13, 117208, C30B 1522
Patent
active
053738080
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for processing dissociative compound semiconductors and their single crystals such as GaAS, containing a high vapor pressure component used for making laser elements and IC substrate materials.
2. Technical Background
An example of an apparatus for processing a compound material having a high decomposition pressure is an apparatus shown in FIG. 15 which is disclosed in a Japanese Patent 1,490,669. This apparatus is used to produce a single crystal of a compound semiconductor material, such as GAS containing a high vapor pressure component, by a method known as the Czochralski method (CZ method).
In FIG. 15, the reference numeral 1 refers to a hermetic vessel for pulling a single crystal from a melt. The vessel 1 consists of an upper vessel section 2 and a lower vessel section 3 with a sealing material 5 between the upper and lower vessel sections. A push up rod 6 of the lower section 3 is provided with a stress-moderating device 7 so as to keep the stress imposed on the joint section 4 at a suitable value.
In the interior of the vessel 1 is a crucible 9 supported by a susceptor 8, which is rotated by the bottom rod 10. The vessel 1, which houses all of the above components, is heated by heaters 11a, 11b. A vapor pressure control section 12 is provided on the ceiling section of the upper vessel section 2. The interior wall temperature of the vapor pressure control section 12 is kept at a lower suitable temperature compared with the interior wall temperatures of the vessel 1. The vapor pressure within the vessel 1 is kept at a suitable constant pressure by condensing and adjusting the vapor pressure of the high vapor pressure component, thereby keeping the vapor pressure constant within the vessel 1 and maintaining the stoichiometry of the melt 13 in the crucible 9.
A view rod 14 for observing the growing section of a single crystal 18 is provided through the ceiling section of the vessel 1. The pulling rod 15 and the bottom rod 10 pass through a rotating seal 16 containing a liquid sealant such as B.sub.2 O.sub.3. The entire configuration presented above is housed in an external housing 17.
Next, the method of producing a GAS single crystal using the apparatus described above will be explained. In this case, the high vapor pressure component is As and the other component is Ga.
First, a charge of Ga is placed in the crucible 9, and As feed is placed on the bottom plate section 1a of the vessel 1. After evacuating the entire apparatus, the bottom rod is pushed up to seal the vessel 1.
Next, the interior wall of the vessel 1, excepting the bottom plate section la, is heated by the heater 11a, followed by heating the bottom plate section 1a by the heater 11b, thereby heating the feed of As and subliming the As. Simultaneously, the Ga in the crucible 9 in the vessel 1 is heated to absorb the As vapor and react with the As, thereby synthesizing GAS in the crucible 9.
In this instance, the temperature distribution in the vessel 1 is controlled so that the bottom plate section 1a and the interior wall section of the vapor pressure control section 12 are at lower temperatures compared with those of regions in the vessel 1 so as to prevent As from condensing on the other regions. At the same time, an inert gas is introduced into the external housing 17 to obtain a pressure balance between the interior and exterior atmospheres of the vessel 1.
After completing the synthesizing step of the GAS melt 13 in the crucible 9, a single crystal seed A fixed to the bottom end of the pulling rod 15 is first immersed in the GAS melt, and then the seed A is rotated and pulled up by the pulling rod 15 while the temperature of the heaters 11a and 11b are lowered to grow a single crystal 18 as illustrated in FIG. 15.
The amount of As feed placed on the bottom plate section 1a of the vessel 1 is a sum of: the amount required to synthesize the GAS melt; the amount to fill the interior space of the vessel 1 as a gas at a ce
REFERENCES:
patent: 4750969 (1988-06-01), Sassa et al.
patent: 4761202 (1988-08-01), Bordui et al.
patent: 4874458 (1989-10-01), Nishizawa
patent: 4904336 (1990-02-01), Ozawa et al.
patent: 5091043 (1992-02-01), Shirata et al.
Atami Takashi
Sassa Koichi
Shirata Keiji
Breneman R. Bruce
Garrett Felisa
Mitsubishi Materials Corporation
Research Development Corporation of Japan
Zaidan Hojin Handotai Kenkyu Shinkokai
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